A great advantage of thin flexible glass is that it is capable of being processed roll to roll. In most applications it must be coated, and since optical coatings are generally hard and brittle and crack easily when flexed, they can be problematic in roll to roll processes. There are few detailed accounts of coatings that overcome this barrier. The immediate subject of this paper is a conductive coating that also reduces reflectance. Conductive layers are a common feature and most often maximum transmittance through their glass substrate is also required. The most important property of this paper is that it gives a complete, detailed description of the coating, the substrate, and the sputtering and annealing processes, details that are, sadly, not always entirely revealed. However the coating design itself is also of interest. The low-index material is AlSiO2
with an index not far from that of SiO2
and a little lower than that of the substrate, but the high-index material is the conductive ITO itself, with an index in the middle of the visible of around 1.7, rather lower than usual in a straightforward antireflection coating. The design was achieved by optimization, but we can recognize a flattening, close to halfwave, layer next to the substrate, which works because it has a slightly lower index, but which also serves as a buffer between the ITO and the substrate, followed by what is close to the well-known two-material four-layer antireflection coating for the visible. This is an important and interesting paper.
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